Alfalfa ranks the first among forage crops in arid areas of the middle east, where irrigation water is limited, and conservation of it is of great concern. An experiment was conducted to study the effect of P fertilizer combined with irrigation intervals on yield parameters and protein content of alfalfa. During two years, three P levels (0, 25, 50 kg P /ha/cut) and two irrigation interval treatments (5,10 days) through seven cuts a year were applied. Studied parameters were forage fresh yield (FFY), forage dry yield (FDY), dry matter percentage (DM%), crude protein percentage (CP%), and crude protein yield (CPY). The results showed that increasing P application increased fresh, dry and protein yield significantly. Little decrease but significant in fresh, dry and protein yield was associated with increasing irrigation inter-vals. Increasing P fertilizer compensated for the effect of increasing irrigation intervals.